1. Field of the Invention
The present invention relates to an apparatus for driving a steering shaft in a motor-driven power steering system, which is capable of performing a starting function and a steering force improvement function of a vehicle by using one single motor.
2. Description of Related Art
Generally, a vehicle with a motor-driven power steering system (hereinafter, referred to as ‘MDPS’) separately has a starter motor for starting the vehicle and a MDPS motor for improving steering force.
When a starting signal is inputted into a magnet switch, the starter motor is driven. A pinion gear is rotated by rotation force of the starter motor and a flywheel ring gear is rotated by rotation force of the pinion gear.
The flywheel ring gear is connected to a crankshaft and the crankshaft is connected to a piston of an engine, thereby starting the vehicle.
When a driver rotates a steering wheel after starting the vehicle, a torque sensor detects a steering angle of the steering wheel and transmits a signal thereof to an ECU (Electronic Control Unit). The ECU drives the MDPS motor by using information inputted from the torque sensor. A steering shaft is rotated by driving the MDPS motor, thereby improving the steering force.
However, since the starter motor is not separately used after starting the starter motor, a structure in which the vehicle with the MDPS separately has the starter motor and the MDPS motor is very inefficient in consideration of securing of a narrow space of and an installation space of an engine compartment, and manufacturing cost.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.